Generally, as is known in the prior art, in the field of centrifugal weight advance mechanisms for ignition distributor assemblies, the centrifugal weights are held in place at relatively low engine speeds by the action or resistance of a primary spring acting through a moment arm. When engine speed is increased the centrifugal force moves the centrifugal weights generally radially outwardly from the center of rotation. Such outward movement of the centrifugal weights caused an extension, or additional loading, of the primary spring while at the same time increasing the effective length of the associated moment arm against which the spring reacted. The overall geometry of the coacting elements and the spring was such as to result in a linear relationship as between the degrees of spark or ignition advance and the speed of rotation of the distributor drive shaft. Further, it has been known that by changing the said geometry the relationship between the degrees of ignition advance and speed of rotation of the distributor drive shaft (engine speed) can be changed from a purely linear relationship.
As has already been indicated, in such prior art distributors two weights were used. One of such weights was attached to the primary spring while the other of such weights was attached to a secondary spring. The two weights were, in turn, operatively connected to each other through a suitable mechanical linkage. Such arrangements almost invariably created large internal forces in the overall mechanism resulting in mechanical hysteresis which is a serious and undesirable characteristic in any ignition distributor.
Accordingly, the invention as herein disclosed and described is primarily directed to the solution of the above and other attendant problems.